More evidence that vitamin D requirements are much, much higher than traditionally recommended amounts

Back in December, one of my blogs focused on research which sought to determine the intakes of vitamin D required to maintain certain concentrations of this nutrient in the body [1]. This particular study found that to maintain a vitamin D level of 80 nmol/L (32 ng/ml) about 1600 IU is required. You can read the whole blog post here.

Some regular readers may know that I have, for the last few months, been attempting to optimise my own vitamin D levels. Earlier in the year, I had my levels measured for the first time ever and these came back at 15 ng/ml (very low). I started supplementing with vitamin D at a dose of 3000 IU per day and about 10 weeks later, my levels had increased to 31 ng/ml. The 3000 IU I was taking was roughly twice what I theoretically needed to maintain this level of vitamin D [1]. Perhaps my need for vitamin D was greater than others? Reading a letter published on-line in the American Journal of Clinical Nutrition this week, I’m not so sure.

In this letter [2], Dr Reinhold Vieth from Mount Sinai hospital in Toronto criticises the mathematical extrapolation on which previous research [1] was based. Dr Vieth claims that this inappropriate methodology has led to an underestimation in vitamin D requirements. In support of this he cites three studies (two, his own) in which individuals were actually supplemented with vitamin D to see what blood levels were achieved [3-5]. According to this research (in both younger and older adults), to maintain a blood level of 32 ng/ml requires 4000 IU (100 mcg) of vitamin D per day.

These levels are much more in line with my own, recent experiences. But much more importantly, they again demonstrate that the traditionally recommended vitamin D levels are quite inadequate. 4000 IU per day is 10 times the amount usually recommended, and this is to achieve a blood level that some would stay is still a way off optimal.


1. Cashman KD, et al. Estimation of the dietary requirement for vitamin D in healthy adults. Am J Clin Nutr 2008;88:1535-1542.

2. Vieth R. Experimentally observed vitamin D requirements are higher than extrapolated ones. Am J Clin Nutr 26th August 2009 [epub ahead of prin publication]

3. Vieth R, et al. Randomized comparison of the effects of the vitamin D3 adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients. Nutr J. 2004;19;3:8.

4. Vieth R, et al. Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level. Am J Clin Nutr. 2001;73(2):288-94.

5. Mocanu V, et al. Long-term effects of giving nursing home residents bread fortified with 125 microg (5000 IU) vitamin D(3) per daily serving. Am J Clin Nutr. 2009;89(4):1132-7.

9 Responses to More evidence that vitamin D requirements are much, much higher than traditionally recommended amounts

  1. Peter Silverman 1 September 2009 at 3:22 pm #

    Dr. Wm Davis claims that D3 tablets don’t work, but the gelcaps do.
    He says he has tested thousands of people’s levels and put many of them on supplements. It would be an awfully easy study to do.

  2. Chris 2 September 2009 at 9:46 am #

    “It would be an awfully easy study to do”

    ..and foolish not to commission if low levels of vitamin D have health and metabolic implications?

  3. M. Cawdery 4 September 2009 at 11:37 am #

    There is some evidence that the important Vit D is D3. Vitamin D is derived from cholesterol and is therefore likely to be depleted along with cholesterol by STATINS. Nobody has monitored Vit D3 in the big clinical studies involving statins but then the Gospel is that cholesterol is the danger – nothing else matters.

    Anyone interested should check Dr Graveline (ex NASA pilot/doctor) has extensively researched the adverse reactions to statins and their metabolic associations

  4. Terry 4 September 2009 at 12:16 pm #

    I’ve been taking 50,000 IU per day capsules from for the past year on the recommendation of Dr Joe Prendergast at He’s been taking this amount for the past ten years – with only good effects, no bad ones. Ditto for me.

  5. Hilda Glickman 4 September 2009 at 2:54 pm #

    I read somewhere that fair skinned people absorb more vit D from the sun than dark skinned people. This makes sense as many fair skinned have genes from people who lived in colder climates with less sun. So maybe what this also means is that dark skinned people (including Caucasians) need more sun (or vit D supps) if they live in cold, wet UK (even more if in Scotland). Hilda

  6. Antje 4 September 2009 at 3:18 pm #

    My experience is different! After reading your blogs on Vit. D i had mine tested. For years i have taken 400mcg only and i bougt the cheapest brand. I do use sunscreen (be it the organic variety- Weleda or Dr. Hauschka so no carcinogens there)) and although i do hike and cycle often it is basically an indoorlife i am leading. So i was a bit worried about my vit.D level. I started taking cod liver oil one spoon daily and stopped the tablets. After 6 weeks i did the test and the result is 123nmol/l! Maybe it helps that i eat herring and mackerel 3 to 4 times a week and have done that all my life (am 56 now)

    Thank you very much for this interesting newsletter!

  7. Danica 6 September 2009 at 11:12 am #

    Hello Dr Briffa

    I am writing a book at the moment which is a journey through diabetes. My son was diagnosed two years ago and all my findings through this journey will be in this book. I am not sure yet what the rules and regulations are regarding copywright but was wondering if it would be ok if I used some of the blogs to support my findings. Please, please, please help 🙂

  8. Emma 6 September 2009 at 9:58 pm #

    I’ve found that a very easy, convenient way to take larger doses of vitamin D is in a liquid form – Biotics Research make a product called Bio-D Mulsion Forte in which the vitamin D3 is dispersed within an acacia and sesame oil emulsion and delivers 2000IU per drop, which makes it very easy to take high doses, rather than having to take lots of capsules. You simply put the drop onto the end of your finger and then into your mouth, ideally under the tongue.

    You can buy this products through nutri-link

  9. Peter Andrews 21 November 2009 at 12:48 am #

    I am a big advocate for vitamin D and personally take 5000 IU/day except during summer.

    Regarding commenter Terry taking 50,000IU/day — I have researched a lot and have never heard anyone advocate that much. The best research indicates the maximum safe daily dose is 10,000IU/day.

    For anyone interested in taking vitamin D, I suggest that they consider taking 100mcg of vitamin K2. Read Vitamin D toxicity redefined: vitamin K and the molecular mechanism by Chris Masterjohn.

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